CHICAGO – The Council on Tall Buildings and Urban Habitat (CTBUH) and the Chicago Architecture Foundation (CAF) held the second of the four-part “Building Tall” series, continuing the momentum established by the first event just two months prior. This second event, which was kindly sponsored by Olsson Fire & Risk, focused the conversation on “Securing Tall,” posing the question: What is the Biggest Threat to a Skyscraper?

To attempt an answer, the event brought together a diverse group of experts representing different avenues of skyscraper security, including fire engineering, structural engineering, architecture / climate, and academia. Each panelist delivered a rapid-fire presentation before engaging in a lively dialogue with each other and the audience. Panelists included Simon Lay, Director, Olsson Fire & Risk; Don Davies, President, Magnusson Klemencic Associates; Nicole Dosso, Director, Skidmore, Owings & Merrill (SOM), and CTBUH Executive Director Dr. Antony Wood, who moderated the event.

Dr. Wood opened the event with an overview of the topic before introducing the three other speakers and explaining their diverse backgrounds and approaches to the topic. Simon Lay presented first with a look at fire risks, saying “Fire is something which is pretty innate to all of us, and we have a natural fear of fire that is built into us.” However, Lay cautioned that the risk of fire is amplified in the media, and that proper building analyses and fire engineering can do much to mitigate the issue. Thus, he focused his presentation not on direct fire risks, but rather the risks that can arise from following building codes too closely and thereby ignoring problems that can lead to unnecessary fire risks. With this line of thinking, Lay emphasized the importance of probabilistic fire engineering analyses over traditional prescriptive building codes, reflecting how contemporary buildings have surpassed the limits of code requirements through expressive forms, complex internal programming, and sheer height.

Next up, Don Davies focused the group’s attention on risks related to tall building structures. He began by dividing the broad topic into the many individual forces that pose risks to skyscrapers – starting with gravity. Davies noted that although gravity is universal and relatively easy to quantify, its effects over time are difficult to determine. He next turned to seismic hazards, which, unlike gravity, vary based on location. He argued that this increased risks because buildings are not designed to the same requirements, noting specifically the risk posed from falling cladding materials during an earthquake.

Davies also spoke about wind-related risks and the reality that wind storms are likely to rise in intensity. Here, he noted that although life-safety precautions remain strong, the economic impact of major wind storms can be costly, returning to an earlier point that perhaps economics are actually the greatest risks to skyscrapers. “Bottom line for me, it’s economics,” Davies concluded, “because most of the issues I’ve [explored] we can manage the hazard of.”

This final point dovetailed nicely with Nicole Dosso’s presentation, who described the complexities of designing One World Trade Center with an eye for robust security, and how that intensified the challenges of cleaning up after Hurricane Sandy. Dosso began by exploring the challenges of the One World Trade Center design, noting in particular the lack of vehicular access on-site and glass in the lobby.

Her presentation also looked at the after-effects of Hurricane Sandy on the World Trade Center site and the economic and logistical challenges posed by the clean-up efforts and magnified by the building design. She focused on the basement flooding caused by the hurricane, and the changes to the building that were required, including new, water-tight barriers and the relocation of critical infrastructure to higher ground. She concluded by pointing to the importance of learning from these experiences, saying “Architects and engineers need to look at the challenges of today as design opportunities and invent ways to create great civic spaces that are secure, safe, and resilient.”

Nicole Dosso, Director, Skidmore, Owings & Merrill (SOM), addressedthe role of security in the design of One World Trade Center.

A wide-ranging panel discussion encompassed a number of the topics mentioned in the presentations along with questions posed by the audience.

Next, Wood took the podium to round-out the discussion on building threats with a number of alternative observations. Among other topics, Wood discussed professional incompetence as a serious concern, citing a project in Shanghai that collapsed due to human error. He also mentioned the challenges posed in unfinished or never-completed buildings, referring to the "Torre David" in Venezuela, which became a dangerous slum after construction halted due to a financial downturn. He next discussed building life cycles, raising a number of questions about how to plan for aging buildings and functional obsolescence.

He concluded with a look at the impact of climate change, and the concern that all the problems mentioned by all speakers are poised to get worse as the world’s climate becomes more volatile. With this in mind, he posed a final concern, saying: “I just wonder if humanity at some point in the future will see a time where we begin to realize that certain cities are unviable” because of climate change.

Following the event, guests were given the opportunity to mingle and engage in deeper discussions with the panelists.

The wide-ranging panel discussion that followed encompassed a number of the topics mentioned in the presentations along with questions posed by the audience. Climate change naturally drove much of the early conversation, with panelists discussing the ways that skyscrapers can adapt to a changing environment, touching on techniques that are already in practice today, like raising buildings on stilts. As Dosso observed, developers are “no longer interested in the 100-year flood plain; there looking at a 500-year flood plain.” This longer-term planning, she argued, was a direct result of catastrophic weather events like Hurricane Sandy.

This discussion prompted a question of urban vitality if buildings eschew the ground-plane. Davies noted that an open ground-plane can be filled with small-scale infrastructure and amenities, “If you can open up the ground-plane to what may be more transient infrastructure that’s not meant to last long...it’s easier to repair [in a hazard], and there may actually be an easy combination between the two.” This type of practical, solution-oriented thinking dominated the conversation.

As the discussion came to a close, those in attendance felt that the conversation accurately summed up the variety of challenges and risks that tall buildings face. While no particular hazard was named “the biggest threat,” the specter of climate change and economic downturn stood out as the biggest potential challenges for tall buildings moving forward.